Comparative studies of the properties of the polypeptides obtained from normal and mutant hemoglobin will be expanded to the acid base titration of the Beta(1-55) peptides obtained from hemoglobin H and S. A different conformation has been observed in the Beta(1-55) peptide from hemoglobin S, when compared to the correspondent peptide from hemoglobin A. This could shift the pk of ionization of the only histidine present in the Beta(1-55) peptides. The Beta(56-146) peptide has a large amount of helical content. Its tertiary structure will be investigated with experiment of life-time fluorescence, using a probe that specifically reacts with the cysteine. Reconstitution with the heme will be attempted and if positive, the kinetic of the reaction will be studied. The possible interaction with the alpha subunits will be investigated. We are in the process of preparing the alpha(104) and alpha(105-141) peptides. Their secondary and tertiary conformation will be investigated with measurement of optical activity, heme reconstitution, interaction with the partner Beta subunits.